Method and system for detecting particulate matter in exhaust gases

Abstract

Fine dust sensor arrangement (202) comprising the following: a spherical arrangement (204); a support rod (208) coupled to a lower end of the spherical arrangement (204); several flow tubes (206) coupled to an upper end of the spherical arrangement (204); and a sensor element (234) which is positioned distal to the multiple flow tubes (206) within the spherical arrangement (204).

Description

Area

[0001] The present application relates to the detection of fine dust particles in an exhaust system. Background / Brief description

[0002] Engine emission control systems may utilize various exhaust gas sensors. An example sensor may be a particulate matter sensor that indicates the mass and / or concentration of particulate matter in the exhaust gas. In one example, the particulate matter sensor may operate to accumulate particulate matter over time and provide an indication of the degree of accumulation as a measure of the level of particulate matter in the exhaust gas. The particulate matter sensor may be located upstream and / or downstream of a diesel particulate filter and may be used to detect the particulate matter load of the particulate filter and diagnose the operation of the particulate filter.

[0003] US 2011 / 0 010 071 A1 discloses a system for particulate matter sensor signal processing, comprising a particulate matter sensor arrangement including an optical particulate matter sensor and a particulate matter charge sensor, which are arranged together in an exhaust gas pipe. The particulate matter charge sensor has, for example, a cylindrical, rod-shaped electrode, the end of which can be shaped like a ball for signal optimization. The optical particulate matter sensor, in particular, has two rod-shaped optical fibers with a light source and a light detector, which extend into the pipe at a 90-degree angle so that the detector receives more or less scattered light from the light source, depending on the particulate matter content in the exhaust gas.

[0004] DE 10 2013 207 630 A1 describes an optical sensor for measuring the concentration of exhaust gas components. Light exits an optical fiber and, after passing through a measuring region in the exhaust gas flow, enters another optical fiber. It is shown that the exhaust gas flow within an exhaust pipe is directed through a tubular sensor, which, for example, has an S-shape. Optical sensor elements such as a light source and a mirror with a measuring region located between them can be arranged in the tubular sensor. Alternatively, a sensor can also be provided that has an inlet region for exhaust gas into the measuring region that faces away from the direction of exhaust gas flow.

[0005] US 2009 / 0 188 300 A1 presents an electrode structure for a particulate matter sensor. The particulate matter sensor has an electrode designed so that the surface area in the area of ​​the electrode tip is enlarged and has, for example, the shape of a star, a twisted shape, a helix, or a ball.

[0006] DE 10 2007 033 215 A1 describes a sensor for detecting the size distribution of particles in a gas stream. The sensor comprises an electrode system with several electrodes arranged in a plane. Two electrodes of different polarity form an electrode pair. The electrode pairs are arranged along a fictitious beam lying in the plane of the electrodes such that the beam runs between the two electrodes of each electrode pair. The voltage between each electrode pair can be determined individually along the beam.

[0007] Another example of an FS sensor is shown by Maeda et al. in US patent application US 2012 / 0 085 146 A1. Here, the particulate matter sensor is mounted on top of an exhaust pipe and housed within a cylindrical protective tube. The FS sensor additionally includes a sensing element positioned closer to a center of the exhaust pipe so that the sensor output more accurately represents an average soot concentration in the exhaust pipe. Furthermore, the FS sensor includes inlet openings configured to direct exhaust gas into the sensor and to the sensing element. Here, the sensing element is positioned closer to the inlet holes to allow the sensing element to detect more of the incoming particulate matter.

[0008] However, the inventors have identified potential problems with such sensor configurations. For example, such an arrangement may make the sensor element more susceptible to contamination by water droplets in the exhaust gas that condense in or near the intake ports. Such sensor configurations may require an additional protective coating to protect the soot sensor element from direct impact from larger particles and water droplets. An additional protective coating may reduce the electrostatic attraction between the charged soot particles and the sensor element's electrodes and may lead to reduced soot sensor sensitivity. Due to the reduced sensitivity, the soot sensor may not be able to reliably determine particulate filter leakage. Therefore, sensor defects may lead to a false indication of DPF degradation and unjustified replacement of functioning filters.

[0009] On the other hand, if the sensor is mounted at the bottom of the exhaust line, as demonstrated by Paterson in US patent application US 8,310,249 B2, water condensing at the bottom of the exhaust line can overflow into the sensor element and thus contaminate it. Such contamination of the sensor element can lead to fluctuations in the sensor output, reducing the accuracy of the particulate filter's estimated particulate load.

[0010] The inventors herein have recognized the above-mentioned problems and set forth an approach to at least partially solve the problems. In one exemplary approach, a particulate matter sensor is provided for detecting particulate matter in an exhaust passage of an engine. The particulate matter sensor includes a spherical assembly, a support rod coupled to a lower end of the spherical assembly, a plurality of flow tubes coupled to an upper end of the spherical assembly, and a sensing element disposed within the spherical assembly distal to the plurality of flow tubes. In this manner, by isolating the plurality of flow tubes from the sensing element, problems related to water droplets and larger contaminants impacting the sensing element and causing fluctuations in the sensor output can be reduced.

[0011] As one example, an exhaust particulate matter sensor assembly may be positioned downstream of the exhaust particulate filter in an exhaust conduit. The particulate matter sensor may include a spherical assembly having a plurality of flow tubes attached to an upper end of the assembly and a sensor element positioned closer to a lower end of the assembly. Specifically, the spherical assembly may include hollow, spherical, concentric outer and inner devices separated by a gap. A hollow support rod may be installed at the lower end of the assembly, coupling the assembly to the underside of the exhaust conduit. By mounting the assembly to the support rod, the sensor element may be positioned closer to a center of the exhaust conduit.

[0012] The plurality of flow tubes coupled to the top of the assembly may include hollow, cylindrical inner and outer tubes. Thus, the outer tube may be an inlet tube mounted on top of the outer device, and the inner tube may be an outlet tube mounted on top of the inner device and positioned within the outer tube. Additionally, the outer tube may have a plurality of perforations along the curved surface configured to direct the exhaust gas into the gap between the outer and inner devices. The exhaust gas may then be split into two portions; a larger portion of the exhaust gas within the gap may be directed through a hole located on the bottom of the inner device toward the sensor element positioned within the inner device, and a smaller portion may descend toward the bottom of the outer device.Here, a smaller portion may contain particles larger than a threshold size, which can consequently sink towards the bottom of the outer device. However, the hollow rod is fluidly coupled to the outer device. Therefore, the heavier particles in the smaller exhaust portion can flow into the hollow rod and continue to be guided out of the assembly. However, lighter soot particles in the larger exhaust portion can enter the inner device and accumulate on the sensor element. Therefore, the sensor element can in turn be used to diagnose the function of the particulate filter. Here, the sensor element is positioned away from the inlet pipe and can therefore be protected and sensor reliability increased by spacing the sensor element away from the inlet pipe and still providing an alternative path for heavier particles.

[0013] This improves the functionality of the sensor element and makes the sensor more reliable. Furthermore, by enabling more accurate diagnosis of the exhaust particulate filter, exhaust emission compliance can be improved. This reduces the high warranty costs of replacing functioning particulate filters. The exhaust gas can exit the sensor through outlet pipes at the top of the assembly. The symmetrical design of the inlet and outlet pipes eliminates the manufacturing process for specific sensor orientation during installation and improves sensor reproducibility.

[0014] It should be understood that the above summary is provided to introduce, in simplified form, a selection of concepts further described in the detailed description. It is not intended to identify key or essential features of the claimed subject matter, the scope of which is defined solely by the claims following the detailed description. Furthermore, the claimed subject matter is not limited to implementations that address any disadvantages noted above or in any part of this disclosure. Short description of the drawings Fig. Figure 1 shows a schematic representation of an engine and an associated particulate matter (PM) sensor positioned in an exhaust stream. Fig. Figure 2A shows a schematic diagram of the FS sensor, which includes a spherical array with multiple flow tubes and a sensor element mounted by a hollow support rod within an exhaust pipe. Fig. Figure 2B shows a schematic diagram of the FS sensor showing exhaust gas flowing into the FS sensor through flow tubes attached to the top of the spherical assembly. Fig. 3A to 3C show exemplary layouts of circular, finger-like interlaced electrodes formed on a first surface of the sensor element. Fig. 4 shows a heating element formed on a second, opposite surface of the sensor element. Fig. Figure 5 is a flowchart illustrating an exemplary method for collecting particulates in the exhaust stream via the sensor elements disposed within an internal device of the spherical array of the FS sensor. Fig. Figure 6 shows a flowchart illustrating an exemplary method for regenerating the sensor electrodes of the FS sensor. Fig. Figure 7 shows a flowchart depicting an exemplary method for diagnosing leaks in a particulate filter positioned upstream of the FS sensor. Fig. 8 shows an exemplary relationship between the soot load on the FS sensor and a soot load on a particulate filter positioned upstream of the FS sensor. Detailed description

[0015] The following description relates to systems and methods for detecting particulate matter (PM) in an exhaust stream of an engine system, such as the engine system as described in Fig. 1. An FS sensor may be placed in an exhaust tract of the engine system. The FS sensor may include a spherical assembly having a plurality of flow tubes attached thereto, and a support rod attached to diametrically opposite ends of the spherical assembly. The spherical assembly may be mounted to an underside of the exhaust tract using the support rod. Specifically, the spherical assembly includes an inner spherical device positioned within an outer spherical device and separated by a gap, wherein a plurality of flow tubes includes an inner tube positioned within an outer tube and separated therefrom by a space, as shown in Fig. 2A. Furthermore, a circular, spherical element may be positioned in the inner device, and exhaust gas may be directed toward the sensor element by means of perforations and holes formed on the outer tube and the inner device, as shown in Fig. 2B. The sensor element may comprise concentric, finger-like interlaced electrodes formed on a first surface of the sensor element, as shown in the Fig. 3A to 3C. In addition, the sensor element may have heating elements formed on a second, opposite surface, as shown in Fig. 4. A controller may be configured to execute a control routine, such as the example routine from Fig. 5 to accumulate particles in the exhaust gas on the electrodes of the sensor element. Furthermore, the control system can temporarily deactivate the FS sensor ( Fig. 6) to enable continuous FS monitoring. Furthermore, the controller may also be configured to execute a routine, such as an example routine from Fig. 7 to regenerate the exhaust particulate filter based on the time between FS sensor regenerations. An example of the filter diagnostics is shown in Fig. 8. In this way, the functionality of the FS sensor for estimating the filtering capabilities of the DPF (and thereby detecting DPF leaks) can be enhanced.

[0016] Fig. 1 shows a schematic diagram of a vehicle system 6. The vehicle system 6 includes an engine system 8. The engine system 8 may include an engine 10 having a plurality of cylinders 30. The engine 10 includes an engine intake 23 and an engine exhaust 25. The engine intake 23 includes a throttle valve 62 fluidly coupled to the engine intake manifold 44 via an intake passage 42. The engine exhaust 25 includes an exhaust manifold 48 that ultimately leads to an exhaust tract 35 that directs exhaust gas to the atmosphere. The throttle valve 62 may be positioned in the intake passage 42 downstream of a boosting device, such as a turbocharger (not shown), and upstream of an aftercooler (not shown). Thus, the aftercooler, if present, may be configured to reduce the temperature of the intake air compressed by the boosting device.

[0017] The engine exhaust 25 may include one or more emission control devices 70, which may be mounted in a closely coupled position within the exhaust. One or more emission control devices may include a three-way catalyst, a lean NOx trap, an SCR catalyst, etc. The engine exhaust 25 may also include a diesel particulate filter (DPF) 102 positioned upstream of the emission control device 70, which temporarily filters diesel particulate matter from incoming gases. In one example, the DPF 102, as depicted, is a diesel particulate trap system. The DPF 102 may have a monolithic structure, made of, for example, cordierite or silicon carbide, with multiple channels therein for filtering particulate matter from the diesel exhaust.Tailpipe exhaust that has been filtered by FS following passage through the DPF 102 may be measured in an FS sensor 106 and further processed in an emission control system 70 and expelled into the atmosphere via the exhaust tract 35. In the depicted example, the FS sensor 106 is a resistive sensor that estimates the filtering efficiency of the DPF 102 based on a change in conductivity measured at the FS sensor electrodes. A schematic view 200 of the FS sensor 106 is shown in FIG. Fig. 2, as described in more detail below.

[0018] The vehicle system 6 may further include a control system 14. The control system 14 is shown receiving information from a plurality of sensors 16 (various examples of which are described herein) and sending control signals to a plurality of actuators 81 (various examples of which are described herein). For example, the sensors 16 may include an exhaust flow rate sensor 126 configured to measure a flow rate of exhaust gas through the exhaust tract 35, an exhaust gas sensor (located in the exhaust manifold 48), a temperature sensor 128, a pressure sensor 129 (located downstream of the emission control system 70), and an FS sensor 106. Other sensors, such as additional pressure, temperature, air / fuel ratio, exhaust flow rate, and composition sensors, may be coupled to various locations in the vehicle system 6.As another example, the actuators may include fuel injectors 66, throttle body 62, DPF valves that control filter regeneration (not shown), electrical circuit switches, etc. The control system 14 may include a controller 12. The controller 12 may be provided with computer-readable instructions stored in non-transitory memory. The controller 12 receives signals from the various sensors of . Fig. 1, processes the signals and uses the various actuators of Fig. 1 for adjusting engine operation based on the received signals and instructions stored in a memory of the controller. As one example, during operation of the FS sensor to accumulate soot particles, the controller may send a control signal to an electrical circuit to apply a voltage to the sensor electrodes of the FS sensor to trap charged particles on the surface of the sensor electrodes. As another example, during FS sensor regeneration, the controller may send a control signal to a regeneration circuit to close a switch in the regeneration circuit for a threshold time to apply a voltage to the heating elements coupled to the sensor electrodes to heat the sensor electrodes. In this way, the sensor electrodes may be heated to burn off soot particles that have been deposited on the surface of the sensor electrodes.Example routines are described here with reference to the . Fig. 5-7 described.

[0019] Let us now turn to the Fig. 2A, which is a schematic view 200 of an embodiment of a particulate matter (PS) sensor arrangement 202 (such as the PS sensor 106 of Fig. 1). The FS sensor arrangement 202 may be configured to measure FS mass and / or concentration in the exhaust gas and may therefore be connected to an exhaust tract 210 (e.g., such as that shown in Fig. 1) upstream or downstream of a diesel particulate filter (such as the one shown in Fig. 1 shown DPF 102).

[0020] In the schematic view 200, the FS sensor assembly 202 is disposed within the exhaust tract 210, with exhaust gases flowing from downstream of the diesel particulate filter to an exhaust pipe (along the X-axis), as indicated by the arrows 258. The FS sensor assembly 202 includes a spherical assembly 204 (hereinafter used interchangeably with assembly 204) that may be mounted within the exhaust tract 210 by a hollow support rod 208 (hereinafter, hollow support rod may be interchangeably referred to as a support rod, mounting rod, or hollow rod). Additionally, the spherical assembly 204 is coupled to a plurality of flow tubes 206 via an upper portion 262 of the assembly 204 and includes a sensor element 234 positioned within the assembly 204. Herein, the assembly 204 is spherical. As another example, the assembly may be a hollow elliptical structure disposed within the exhaust tract.

[0021] The hollow support rod 208 may extend along the Y-axis in a direction orthogonal to a longitudinal axis of the exhaust tract 210. A length L of the support rod 208 may be much longer than a diameter d of the support rod 208. Further, the support rod 208 may have an upper end 260 and a lower end 270, and the length L may therefore comprise the distance between the upper end 260 and the lower end 270 of the support rod 208. A portion of the lower end 270 may be coupled to a bottom surface 212 of the exhaust tract 210 (and not to a top surface 214 of the exhaust tract 210, for example). As an example, the portion of the lower end 270 of the support rod 208 that extends into the underside 212 of the exhaust tract 210 may be much smaller than the portion 254 of the support rod 208 that remains in the exhaust tract 210. The lower end 270 of the support rod 208 may be installed in the underside 212 of the exhaust tract 210 in a variety of ways.For example, the lower end 270 of the support rod 208 may be inserted, threaded, or held into the bottom surface 212 by additional screws (not shown). The support rod 208 may include a drainage hole 252 located closer to the lower end 270 of the support rod than to the upper end 260. Although shown as a single hole 252, the drainage hole may include multiple holes in some embodiments. The purpose of the drainage hole 252 is to drain particles larger than a threshold size from the FS sensor assembly 202, which is described in more detail below.

[0022] During a cold start of the vehicle, the exhaust gas may not be warm enough to convert water within the exhaust line to vapor (gaseous state), which is why water may continue to remain in a liquid state and collect at the bottom 212 of the exhaust tract 210. By mounting the assembly to the support rod 208 as described below, the FS sensor assembly 202 can be positioned closer to the center of the exhaust tract and the sensor can be protected from water condensing and accumulating at the bottom of the exhaust tract.

[0023] The upper end 260 of the support rod 208 may be coupled to a lower portion of the spherical assembly 204. Therefore, the upper end 260 of the support rod 208 may be open (as indicated by the dashed line in Fig. 2A) to enable fluid coupling between the support rod 208 and the spherical assembly 204. Specifically, the spherical assembly 204 includes a hollow outer spherical device 216 (hereinafter outer device 216) and a hollow inner spherical device 218 (hereinafter inner device 218) concentrically positioned within the outer device 216. The upper end 260 of the support rod 208 may be coupled to a lower portion or end 261 of the outer device 216. As a result, the support rod 208 is fluidly coupled to the outer device 216, specifically to the opening formed in the lower portion 261 of the outer device 216 and the upper end 260 of the support rod 208. It will be appreciated that the support rod 208 is not coupled to the inner device 218, but only to the outer device 216.

[0024] The outer device 216 is a spherical protective device with radius R1. Likewise, the inner device 218 is a spherical protective device with radius R2. The inner device 218 is positioned concentrically within the outer device 216 such that a gap 226 exists between the inner and outer devices. Here, the inner device 218 is smaller than the outer device 216 (e.g., R2 <R1) und der Spalt 226 zwischen der äußeren Vorrichtung 216 und der inneren Vorrichtung 218 ist gleich einer Differenz der Radii der zwei kugelförmigen Vorrichtungen (z. B. R1-R2). Daher kann die innere Vorrichtung 218 durch Schrauben (nicht dargestellt) an der äußeren Vorrichtung 216 gehalten werden, die entlang des Umfangs der äußeren Vorrichtung 216 angeordnet sind, zum Beispiel.The outer device 216 and the inner device 218 may share a common center C and have a common central axis YY' that is perpendicular to the exhaust flow direction (arrow 258) within the exhaust tract 210. The inner device 218 and the outer device 216 may be positioned symmetrically to each other. Together, the inner device 218 and the outer device 216 form the spherical assembly 204 of the FS sensor assembly 202.

[0025] As an example, the length L of the support rod 208 and the radius R1 and R2 of the outer and inner members of the spherical assembly 204 can be selected such that the spherical assembly 204 can be positioned closer to a center of the exhaust tract 210. In this way, by positioning the sensor assembly near the center of the exhaust tract 210, the average soot particle concentration in the exhaust tract 210 can be reliably represented in the sensor assembly. Therefore, the sensitivity of the FS sensor assembly 202 can be increased and the sensor can be made more reliable. Furthermore, by enabling more accurate diagnosis of the exhaust particulate filter, exhaust emission compliance can be improved. Therefore, this reduces the high warranty costs of replacing functioning particulate filters, improves exhaust emissions, and extends the service life of exhaust components.

[0026] As previously mentioned, the spherical assembly 204 includes a plurality of flow tubes 206 attached to the upper portion 262 of the assembly. Specifically, the flow tubes 206 include an outer tube 246 and an inner tube 248. The outer tube 246 is an inlet tube configured to receive exhaust gas from the exhaust tract 210, and the inner tube 246 is an outlet or exit tube configured to discharge exhaust gas from the FS sensor assembly 202 back into the exhaust tract 210. Herein, the outer tube 246 is a hollow cylinder of length L1 with radius R3. Similarly, the inner outlet or exit tube 248 is a hollow cylinder of length L2 with radius R4, disposed coaxially within the outer tube 246 and separated from the outer tube 246 by a space 228. Here, the inner tube 248 is smaller than the outer tube 246 (e.g.R4 <R3) und der Raum 228 zwischen dem inneren Rohr 248 und dem äußeren Rohr 246 ist gleich einer Differenz der Radii der zwei Rohre (z. B. R3-R4). Daher kann das innere Rohr 248 durch Schrauben (nicht dargestellt) am äußeren Rohr 246 gehalten werden, die sich entlang der Seitenoberflächen des äußeren Rohrs 246 befinden, zum Beispiel. Das äußere Rohr 246 und das innere Rohr 248 können eine gemeinsame zentrale Achse Y-Y' teilen, bei der es sich um die zentrale Achse der kugelförmigen Anordnung 204 handelt. Die zentrale Achse Y-Y' verläuft senkrecht zur Abgasströmungsrichtung (Pfeil 258) innerhalb des Auspufftrakts 210, wie zuvor beschrieben.

[0027] The length L2 of the inner tube 248 may be longer than the length L1 of the outer tube 248 (e.g., L2>L1). Therefore, the inner tube 248 traverses the gap 226 formed between the inner device 218 and the outer device 216. The outer tube 246 has an upper surface 272 and a lower surface 276, and the distance between the upper surface 272 and lower surface 276 corresponds to the length L1 of the outer tube 246. Likewise, the inner tube 248 has an upper surface 274 and a lower surface 278, and the distance between the upper surface 274 and lower surface 278 corresponds to the length L2 of the inner tube 248. Here, the lower surface 276 of the outer tube 246 is coupled to the upper portion or end 262 of the spherical assembly 204.Specifically, the coupling between the lower surface 276 of the outer tube 246 and the upper portion 262 of the outer device 216 enables fluid communication between space 228 and gap 226. It will be appreciated that the upper portion 262 of the spherical assembly 204 corresponds to the upper portion of the outer device 216. Therefore, the outer tube 246 is coupled to the outer device 216, but not to the inner device 218 of the spherical assembly 204. In other words, the outer device 216 includes the outer tube 246 and the support rod 208 coupled at diametrically opposite ends or portions of the outer device 216.

[0028] Furthermore, the upper surface 272 of the outer tube 246 is coplanar with the upper surface 274 of the inner tube 248. However, the lower surface 276 of the outer tube 246 is not coplanar with the lower surface 278 of the inner tube 248. Therefore, the lower surface 278 of the inner tube 248 is located a distance (e.g., equal to the gap 226) below the lower surface 276 of the outer tube 246 and is further coupled to an upper portion 268 of the inner device 218. In short, the upper surfaces of the outer tube and the inner tube are coplanar, but they are not coupled to either the outer or inner devices of the spherical assembly and are external to the spherical assembly.However, the lower surface 276 of the outer tube 246 is coupled to the upper portion of the outer device 216, while the lower surface 278 of the inner tube 248 is coupled to the upper portion of the inner device 218. The upper portion 268 of the inner device 218 is located closer to the upper portion 262 of the outer device 216 and farther from the lower portion 261 of the outer device 216. The upper portion 268 of the inner device 218 may be separated from the upper portion 262 of the outer device 216 by a distance equal to the gap 226 between the outer and inner devices, for example. Here, the gap 226 may correspond to the difference in length between the outer and inner tubes (e.g., L2-L1).

[0029] The upper surface 272 of the outer tube 246 may be sealed, while the lower surface 276 of the outer tube 246 may be open (or unsealed), thereby fluidly coupling the outer tube 246 to the outer device 216. Herein, the space 228 formed between the outer tube 246 and the inner tube 248 is fluidly coupled to the gap 226 formed between the outer device 216 and the inner device 218. However, both the upper surface 274 and the lower surface 278 of the inner tube 248 may be open. Therefore, the inner device 218 is fluidly coupled to the inner tube 248 via the lower surface 278 and to the exhaust tract 210 via the upper surface 274, for example.

[0030] The inner device 218 is coupled to the lower surface 278 of the inner tube 248 at the upper portion 268, as previously explained. In addition, a lower portion 266 of the inner device 218 includes a hole (or opening or exit port) 244. Here, the hole 244 is formed on the inner device 218 and diametrically opposite the upper portion 268 of the inner device 218, which is coupled to the inner tube 248. Therefore, the hole 244 is located closer to the lower portion 261 of the outer device 216 and farther away from each of the upper portion 262 of the outer device 216 and the upper portion 268 of the inner device 218.

[0031] Therefore, the plurality of flow tubes 206 are configured to conduct exhaust gas into and out of the spherical assembly 204. Specifically, the outer tube 246 includes a plurality of perforations or holes 250 formed along a curved surface of the outer tube 246 through which exhaust gas enters the spherical assembly 204. Exhaust gas within the spherical assembly exits the assembly through the inner tube 248, as described in detail with reference to Fig. 2B explains.

[0032] Therefore, the outer device 216 may be fabricated as a hollow spherical device with cutouts formed at two diametrically opposite ends (along the Y-Y' axis). In one example, the cutouts may be circular. At an upper end, the radius of the cutout may substantially correspond to the radius R3 of the outer tube 246. At a lower end, the cutout may be smaller and substantially correspond to the diameter d of the hollow support rod 208. The outer inlet tube may be fabricated as a hollow cylinder with radius R3 and length L1 and may be inserted into the upper end of the outer device 216 at the cutout of the upper end of the outer device, for example. Likewise, the support rod 208 may be fabricated as a hollow cylindrical rod with a diameter d and a length L and may be inserted into the lower end of the outer device 216 at the lower cutout.The opposite end of the hollow support rod may be mounted to the underside 212 of the exhaust tract 212 as previously described.

[0033] Similar to the outer device, the inner device 218 may be fabricated as a hollow spherical device with cutouts formed at two diametrically opposite ends (along the Y-Y' axis). At an upper end, the radius of the cutout may substantially correspond to the radius R4 of the inner tube 248. At a lower end, the cutout may result in the hole 244. The inner outlet tube may be fabricated as a hollow cylinder with radius R4 and length L2 and may be inserted first into the outer tube 246 and then into the upper end of the inner device 218 through the upper cutout formed on the inner device 218. Additionally, the inner device 218 may include a sensor element 234 suspendedly coupled within the inner device 218, as described below.

[0034] The sensor element 234 may be suspended closer to the hole 244 using support legs 242. As an example, three support legs 242 (two of three legs are shown in view 200) may be evenly distributed and coupled along the circumference of the inner device 218 (along an inner surface, for example). Therefore, one end of each support leg 242 may be coupled to the inner surface of the inner device 218, and the opposite end of each support leg 242 may be coupled to the sensor element 234. Herein, the length and a spring constant of the support legs 242 may be adjusted to suspend the sensor element 234 at a distance D from the hole 244 formed on the inner device 218.

[0035] The sensor element 234 includes a substrate 240 having interlaced electrodes 236 formed on a first surface and a heating element 238 formed on a second, opposite surface. In other words, the interlaced electrodes 236 and the heating element 238 are formed on two opposite sides of the substrate and are thus separated from each other by a thickness of the substrate 240. Therefore, the sensor element 234 may be a circular element to benefit from the spherical configuration of the assembly 204. However, the sensor element may be rectangular, square, triangular, or the like without departing from the scope of the invention. For a circular element 234, the interlaced electrodes 236 may additionally be circular, thus providing increased surface area coverage of the electrodes formed on the circular sensor element 234.Various other geometries may alternatively be possible without departing from the scope of the disclosure. One example geometry is a finger-interlaced "comb" electrode structure. The soot particles in the exhaust gas may be deposited between the finger-interlaced electrodes, as described with reference to FIG. Fig. 3A-3C. The sensor element 234 can be arranged within the internal device 218 such that the interdigitated electrodes 236 face the hole 244, while the heating element 238, formed on the opposite surface, is further away from the hole 244. The sensor element 234 is positioned away from the flow tubes 206 of the spherical array 204. Thus, by separating the multiple flow tubes from the sensor element, problems caused by water droplets and larger contaminants impinging on the sensor element and causing fluctuations in the sensor output can be reduced. Three example patterns of the circular interdigitated electrodes are shown in FIGS. Fig. 3A-3C. Thus, the description of the electrical circuit and the composition of the sensor element and substrate in the Fig. 3A to 3C are the same.

[0036] With reference to Fig. 3A is a schematic view 300 of a bottom side of the sensor element 234 of Fig. 2A and an accompanying electrical circuit 314. Specifically, the circular interdigitated electrodes formed on a circular substrate 240 are shown. Because the guard assembly is spherical, it may be advantageous to include a circular substrate as the sensing element to increase the surface area available for soot particle adsorption. However, various other substrate and electrode layout geometries are possible without departing from the scope of the invention. Some example layouts include a rectangular or square substrate with interdigitated comb electrodes.

[0037] In view 300, the substrate 240 of the sensor element 234 is circular with a radius R. The substrate 240 of the sensor element 234 may be made of electrically insulating materials. Some examples of possible electrically insulating materials are oxides such as aluminum oxide, zirconium oxide, yttrium oxide, lanthanum oxide, silicon oxide, and combinations thereof, including at least one of the above or similar materials suitable for blocking electrical communication and providing physical protection for the electrodes 306 and 308. In some examples, the substrate 240 may be made of a porous ceramic material (e.g., with a porosity of 60%). The radius R of the circular substrate 240 may be determined based on the radius R2 of the inner device 218 and further adjusted based on the distance D at which the sensor element 234 is suspended above the hole 244, as shown in Fig. 2A.

[0038] The sensor electrode 236 includes a pair of circular, interdigitated electrodes 306 and 308 formed on a surface of the sensor element 234. Herein, the pair of flat, interdigitated electrodes 306 and 308 may form circular, interdigitated prongs, shown by black and gray lines in view 300. These electrodes may typically be made of metals such as platinum, gold, osmium, rhodium, iridium, ruthenium, aluminum, titanium, zirconium, and the like, as well as oxides, cements, alloys, and combinations comprising at least one of the foregoing metals. Each electrode of the interdigitated pair may be made of the same or a different material as the other electrode of the pair. For example, the electrode 306 may be made of the same material as the electrode 308.In another example, electrode 306 and electrode 308 may be made of different materials. The spacing between the circular "prongs" of the two electrodes is typically in the range of 30 micrometers to 50 micrometers, with the linewidth for each individual "prong" being approximately the same, although the latter is not necessary.

[0039] Electrodes 306 and 308 can be connected to an electrical circuit 314 via electrical connections. Electrode 308 of sensor element 234 is connected to a positive pole of a voltage source 316 of electrical circuit 314 via connecting wire 312. Therefore, electrode 308 can be referred to as a positive electrode. Likewise, electrode 306 of sensor element 234 is connected to a measuring device 318 via a connecting wire 310 and is further connected to a negative pole of voltage source 316 of electrical circuit 314. Therefore, electrode 306 can be referred to as a negative electrode. Connecting wires 310 and 312, voltage source 316, and measuring device 318 are part of electrical circuit 314 and are located outside exhaust tract 210 (as an example, less than 1 meter away).Furthermore, the voltage source 316 and the measuring device 318 of the electrical circuit 314 may be controlled by a controller, such as the controller 12 of FIG. Fig. 1, so that particulate matter collected at the FS sensor assembly 202 can be used, for example, to diagnose leaks in the DPF. As such, the measuring device 318 can be any device suitable for measuring a change in resistance (or current) across the electrodes, such as a voltmeter (or an ammeter). As FS or soot particles are deposited between the electrodes 306 and 308, the current measured between the electrodes 306 and 308 may increase, which is measured by the measuring device 318. The controller 12 may be capable of determining the current and deriving an associated FS or soot load on the electrodes 306 and 308 of the sensor element 234 of the FS sensor assembly 202. By monitoring the load on the sensor element 234, the exhaust soot load downstream of the DPF can be determined and thereby used to diagnose and monitor the health and functioning of the DPF.

[0040] In Fig. 3A, the electrode 306 includes a plurality of circular prongs of increasing diameter extending from a center of the substrate 240. The electrode 306 (interchangeable with the negative electrode) includes a substantially straight portion 320 connecting the electrode 306 to the connecting wire 310. Here, the straight portion 320 may extend from the edge (located on the circumference, for example) of the substrate 240 inward toward the center of the substrate 240. As an example, a length of the straight portion 320 may correspond to the radius R of the substrate 240. The electrode 306 may additionally include a plurality of discretely curved portions 324 beginning at discrete locations along the straight portion 320 and extending clockwise along the surface of the substrate 240, terminating at a distance from the straight portion 320.Herein, each curved portion 324 corresponds to a major arc of a circle of a certain radius, with the center coinciding with the center of the substrate 240, for example. As an example, an innermost curved portion of the negative electrode 306 may be formed in the center of the substrate 240. The innermost curved portion of the negative electrode 306 may have a major arc of radius r1. A second curved portion may be formed at a distance w1 from the innermost curved portion and may have a major arc of radius r2, where r2 = r1+w. Likewise, a third curved portion may be formed at a distance w from the second curved portion and may further have a major arc of radius r3, where r3 = r2+w = r1+2w. Similarly, subsequent curved regions may be formed at a distance w, and with increasing radii.Mathematically, the radius of the n-th curved portion 324 of the negative electrode 306 is given by the following equation (1):. rn=r1+(n−1)*w

[0041] The number n of curved sections 324 of the negative electrode 306 formed on the substrate 240 may depend on the radius R of the substrate 240. Therefore, the negative electrode 306 may have a series of curved sections of increasing circumference (e.g., from the center of the substrate). The first innermost curved section of the negative electrode 306 may have a smaller circumference than the second curved section, and so on.

[0042] Similar to the negative electrode 306, the electrode 308 may include a plurality of circular prongs of increasing diameter extending from a center of the substrate 240. The electrode 308 (interchangeable with the positive electrode) includes a substantially straight portion 322 connecting the positive electrode 308 to the connecting wire 312. Here, the straight portion 322 may be parallel to the straight portion 320 of the negative electrode 306 and may extend from an edge (periphery) of the substrate 240 inward toward the center of the substrate 240. As an example, a length of the straight portion 322 of the positive electrode 308 may be equal to, less than, or greater than the length of the straight portion 320 of the negative electrode 306.The positive electrode 308 may additionally include a plurality of discrete curved sections 326 that begin at specific locations along the straight section 322 and extend counterclockwise along the surface of the substrate 240 (away from the straight section 320 of the negative electrode 306) and end at a distance from the straight section 322. Herein, each curved section 326 of the positive electrode 308 corresponds to a major arc of a circle of a specific radius, with the center coinciding with the center of the substrate 240 and the center of the curved sections 324 of the negative electrode 306, for example. As an example, an innermost curved section 324 of the positive electrode 308 may be formed in the center of the substrate 240 and may further include a major arc of radius r1'.Thus, the radius r1' may be greater than the radius r1 of the innermost curved portion of the negative electrode 306 and may be a distance x from the innermost curved portion of the negative electrode 306. A second curved portion of the positive electrode 308 may be formed a distance w' from the innermost curved portion of the positive electrode 308 and may have a major arc of radius r2', where r2' = r1' + w'. In fact, radius r2 = (r1 + w + x). Likewise, a third curved portion of the positive electrode 308 may be formed a distance w' from the second curved portion of the positive electrode 308 and may further have a major arc of radius r3', where r3' = r2' + w' = r1' + 2w'. Similarly, subsequent curved sections of the positive electrode 308 may be formed at a distance w' and with increasing radii.Mathematically, the radius of the m-th curved portion 326 of the positive electrode 308 is given by the following equation (2):. r(m)'=r1'+(m−1)*w'

[0043] The number m of curved sections 326 of the positive electrode 308 formed on the substrate 240 may depend on the radius R of the substrate 240, for example. In this way, the positive electrode 308 may be interdigitated with the negative electrode 306. In one example, the distance w between the negative electrodes may be equal to the distance w' between the positive electrodes. In another example, the distance w may be different than the distance w'. As previously mentioned, various geometries of the interdigitated electrodes may be possible. Fig. Figure 3B shows an example design of the circular, finger-like interlaced electrodes.

[0044] With reference to Fig. 3B is a schematic view 350 of the first surface of the sensor element 234 of Fig. 2A and the accompanying electrical circuit 314. As previously mentioned, the details of the substrate 240, the electrical circuit 314 and the electrical connecting wires 310 and 312 are similar to those described with reference to Fig. 3A. Briefly, the substrate 240 is made of porous electrically insulating materials and may be circular. The sensor element 234 has a pair of circular, interdigitated electrodes 352 and 356 formed on a surface of the sensor element 234. Herein, the pair of flat, interdigitated electrodes 352 and 356 may form circular, interdigitated prongs, shown by black and gray lines in view 350. The details of the electrodes 352 and 354 may be similar to those of the electrodes 306 and 308, as previously discussed with reference to Fig. 3A. Briefly, the electrodes 352 and 354 may be made of metals such as platinum, gold, and the like, as previously described, and may further be connected to the electrical circuit 314 via electrical connections. The electrode 354 of the sensor element 234 is a positive electrode connected to the positive terminal of the voltage source 316 of the electrical circuit 314 via the connecting wire 312. Likewise, the electrode 352 of the sensor element 234 is a negative electrode connected to the positive terminal of the voltage source 316 of the electrical circuit 314 via the connecting wire 310. As previously explained, the electrical circuit 314 and the connecting wires 310 and 312 are housed outside the exhaust tract 210 (as an example, <1 meter away). As previously explained, the voltage source 316 and the measuring device 318 of the electrical circuit 314 may be controlled by a controller, such as the controller 12 of Fig. 1, so that particulate matter collected at the FS sensor assembly 202 can be used to diagnose leaks in the DPF.

[0045] Similar to the negative electrode 306 from Fig. 3A, the negative electrode 352 includes a plurality of circular prongs of increasing diameter extending from a center of the substrate 240. The negative electrode 352 includes a substantially straight portion 358 connecting the negative electrode 352 to the connecting wire 310. Here, the straight portion 358 begins at a point along the circumference of the substrate 240 and extends horizontally inward toward the center of the substrate 240. The negative electrode 352 additionally includes a plurality of discrete curved portions 360 formed along the substrate. Here, each curved portion 360 corresponds to a major arc of a circle of a particular radius, with the center coinciding with the center of the substrate 240. Additionally, the straight portion 358 may intersect each of the curved portions 360 of the negative electrode 352 at midpoints along the major arc, for example. Similar to the negative electrode 306 of Fig. 3A, from equation (1), the radius of the n-th curved section can be mathematically represented by r(n) = r1+(n-1)*w, where r1 is the radius of the innermost curved section 360 and w is the distance between the subsequent curved section 360 of the negative electrode 352.

[0046] Similar to the positive electrode 308 from Fig. 3A, the positive electrode 354 has a plurality of circular prongs of increasing diameter from a center of the substrate 240. In contrast to the positive electrode 308 of Fig. 3A, the positive electrode 354 includes a substantially straight portion 356 connecting the positive electrode 354 to the connecting wire 312. Herein, the straight portion 356 begins at a point along the circumference of the substrate 240 that is diametrically opposite the origin point of the straight portion 358 of the negative electrode 352. Additionally, the straight portion 356 may extend horizontally inward toward the center of the substrate 240. The negative electrode 352 may additionally include a plurality of discrete curved portions 362 formed along the substrate. Herein, each curved portion 362 corresponds to a major arc of a circle of a particular radius, with the center coinciding with the center of the substrate 240, for example. Additionally, the straight portion 356 may intersect each of the curved portions 362 at midpoints along the major arc, for example.Herein, the main arcs of the positive electrode 354 may be opposite the main arcs of the negative electrode 352. Therefore, the ends of the main arcs of the positive electrode 354 may be diametrically opposite the ends of the main arcs of the negative electrode 352. Similar to the positive electrode 308 of FIG. Fig. 3A, the radius of the m-th curved section can be mathematically represented by r(m)' = r1' + (m-1) * w', where r1' is the radius of the innermost curved section 362 and w' is the distance between the subsequent curved sections 362. In this way, a pair of concentric, finger-like interlaced electrodes is formed on the circular substrate 240. In one example, the distance w between the negative electrodes may be equal to the distance w' between the positive electrodes. In another example, the distance w may be different than the distance w'. In the Fig. 3A and Fig. 3B, the electrodes consist of discrete main arcs arranged to form the finger-like interlaced pattern. However, it is also possible to form the finger-like interlaced electrodes using continuous electrodes, as shown in Fig. 3C.

[0047] With reference to Fig. 3C is a schematic view 375 of the first surface of the sensor element 234 of Fig. 2A and the accompanying electrical circuit 314. As previously mentioned, the details of the substrate 240, the electrical circuit 314 and the electrical connecting wires 310 and 312 are similar to those described with reference to the Fig. 3A and Fig. 3B. Briefly, the sensor element 234 may be formed on a circular substrate 240 made of a porous, electrically insulating material. The sensor element 234 includes a pair of spiral, finger-shaped interleaved electrodes 376 and 378 formed on the first surface of the sensor element 234. Herein, the pair of spiral, finger-shaped interleaved electrodes 376 and 378 are shown by black and gray lines in view 375. The details of the electrodes 376 and 378 are similar to those of the electrodes 352 and 354 and the electrodes 306 and 308, as previously described with reference to Fig. 3A or Fig. 3B. Briefly, the electrodes 376 and 378 may be made of metals such as platinum, gold, and the like, as previously described, and may further be connected to the electrical circuit 314 via electrical connections. The electrode 376 of the sensor element 234 is a positive electrode connected to the positive terminal of the voltage source 316 of the electrical circuit 314 via the connecting wire 312. Likewise, the electrode 378 of the sensor element 234 is a negative electrode connected to the positive terminal of the voltage source 316 of the electrical circuit 314 via the connecting wire 310. As previously explained, the electrical circuit 314 and the connecting wires 310 and 312 are housed outside the exhaust tract 210 (as an example, <1 meter away). As previously explained, the voltage source 316 and the measuring device 318 of the electrical circuit 314 may be controlled by a controller, such as the controller 12 of Fig. 1, so that particulate matter collected at the FS sensor assembly 202 can be used to diagnose leaks in the DPF.

[0048] The positive electrode 376 has a straight section 380 and a curved section 384 that begins at one end of the straight section 380 and spirals inward along the circumference of the substrate with a decreasing curvature toward the center of the substrate 240. Likewise, the negative electrode 378 has a straight section 382 at a distance w from the straight section 380 of the positive electrode 376. Additionally, the negative electrode 378 has a curved section 386 that begins at one end of the straight section 380 and spirals inward along the circumference of the substrate with a decreasing curvature toward the center of the substrate 240. Herein, the distance between the curved portion 384 of the positive electrode 376 and the curved portion 386 of the negative electrode 378 is equal to the distance w between the straight portions 380 and 382 of the positive and negative electrodes.

[0049] As an example, during operation of the FS sensor to collect soot particles, the controller may send a control signal to the electrical circuit 314 to apply a voltage to the electrodes 376 and 378 of the sensor element 234. The charged soot particles may then be trapped between the spiral positive electrode 376 and the spiral negative electrode 378. Likewise, the finger-like interlaced electrodes of the sensor element may have a layout that is similar to the layout of Fig. 3A or Fig. 3B, wherein the charged soot particles may be trapped between electrodes 306 and 308 or electrodes 352 and 354. As previously explained, the current measured between the electrodes may increase as soot particles are deposited between the electrodes, as measured by measuring device 318. Controller 12 may be able to determine the current and derive an associated FS or soot load on the electrodes of sensor element 234. By monitoring the load on sensor element 234, the exhaust soot load downstream of the DPF may be determined and thereby used to diagnose and monitor the health and functioning of the DPF. However, if the soot load on the sensor is higher than a threshold, sensor element 234 may need to be regenerated.Herein, the heating elements coupled to the second surface sensor element 234 may be operated to burn accumulated soot particles on the surface of the sensor element 234, as shown in . Fig. 4. For example, if the first surface having the finger-like interlaced electrodes is a lower surface, the second surface of the sensor element having the heating elements is an upper surface. The sensor element can be mounted such that the lower surface is closer to the hole 244 of Fig. 2A. However, if the first surface having the finger-like interlaced electrodes is an upper surface, the second surface having the heating elements is a lower surface and the sensor element can be inverted so that the upper surface is closer to the hole 244 of Fig. 2A is.

[0050] With reference to Fig. 4 is a schematic view 400 of a second surface of the sensor element 234 of Fig. 2A, which has a heating element 402. Here, the second surface is opposite the first surface, which has the finger-like interlaced electrodes, as described with reference to the Fig. 3A to 3C, for example. Therefore, the electrodes and heating elements are formed on opposite surfaces of the sensor element, separated from each other by the thickness of the sensor element's substrate, for example.

[0051] Heating element 402 may include, but is not limited to, a temperature sensor and a heater. Possible materials for the heater and the temperature sensor forming the heating element may include platinum, gold, palladium, and the like; and alloys, oxides, and combinations comprising at least one of the foregoing materials, with platinum / aluminum oxide, platinum / palladium, platinum, and palladium. In view 400, heating element 402 is a circular element with a radius smaller than the radius of sensor element 234, for example. Various other geometries may be possible without departing from the scope of the disclosure. Example geometries include rectangular, triangular, square, finger-like interleaved electrodes, and the like. Heating element 402 may be used to regenerate sensor element 234.Specifically, under conditions where the particulate matter load or soot load of the sensor element 234 is higher than a threshold, the heating element 402 may be operated to burn accumulated soot particles from the surface of the sensor element.

[0052] During FS sensor regeneration, the controller 12 may send a control signal to a regeneration circuit 404 to apply a certain voltage to the heating element. For example, the regeneration circuit may be part of the electrical circuit 314 of the Fig. 3A-3C and may include an additional voltage source 406, a switch 408, and connecting wires 410 and 412 connecting the voltage source 406 to the heating element 402. As one example, the controller may send a control signal to close the switch 408 in the regeneration circuit 404 for a threshold time to apply voltage to the heating element 402 to increase the temperature of the heating element 402. Consequently, when the sensing element 234 is sufficiently clean, the controller 12 may send a control signal to open the switch 408 in the regeneration circuit 404 to stop heating the heating element 402. By intermittently regenerating the sensing element 234, it may be returned to a condition (e.g., uncharged or only partially charged condition) more suitable for collecting exhaust soot.In addition, precise information regarding the exhaust soot level can be derived from the sensor regeneration and this information can be used by the controller to diagnose leaks in the particulate filter, as shown in . Fig. 8 explained.

[0053] Therefore, the example particulate matter sensor assembly includes a spherical assembly, a support rod coupled to a lower end of the spherical assembly, a plurality of flow tubes coupled to an upper end of the spherical assembly, and a sensor element disposed within the spherical assembly distal from the plurality of flow tubes. Additionally or alternatively, the spherical assembly includes a hollow inner device concentrically positioned within a hollow outer device, the inner device separated from the outer device by a gap. Additionally or alternatively, the plurality of flow tubes may include an outer cylindrical tube and an inner cylindrical tube coaxially disposed within the outer tube, wherein a length of the outer tube is less than a length of the inner tube.Additionally or alternatively, the outer tube may be mounted at the upper end of the spherical assembly through the hollow outer device. Additionally or alternatively, the outer tube may have a plurality of perforations configured to receive exhaust gas from an exhaust tract, wherein the exhaust gas is received in the gap between the outer device and the inner device in a direction orthogonal to a plane of the sensing element, wherein the exhaust gas can then be directed through the gap to a hole formed along a lower portion of the inner device, the hole being configured to direct the exhaust gas from the gap into the inner device toward the sensing element in a direction opposite to an exhaust gas flow direction through the gap.Additionally or alternatively, the sensor element may comprise a pair of circular, finger-like interlaced electrodes formed on a first surface and a heating element formed on a second, opposite surface, wherein the sensor element is floatingly coupled within the internal device by support legs coupled to the internal device such that the pair of circular, finger-like interlaced electrodes face the hole on the internal device, and wherein the pair of circular, finger-like interlaced electrodes comprise finger-like interlaced, spiral positive and negative electrodes.Additionally or alternatively, the inner tube may be mounted at the top of the spherical assembly by a hollow inner device such that the inner device traverses the gap in the spherical assembly, wherein exhaust gas received by the outer tube and directed into the inner device can be discharged through the inner tube into the exhaust tract. Additionally or alternatively, the support rod may be hollow and couple the spherical assembly to a bottom of an exhaust tract, wherein the support rod may be configured to direct an exhaust portion received in the gap into the exhaust tract through a drainage hole of the support rod, the drainage hole being positioned proximate the bottom of the exhaust tract, the exhaust portion comprising exhaust particulates having a size larger than a threshold size.

[0054] With reference to Fig. 2B, the schematic view 290 shows the exhaust flow through the FS sensor assembly 202. Specifically, view 290 shows the exhaust flowing into the FS sensor assembly 202 through the plurality of perforations 250 formed along the curved surface of the outer tube 246. Herein, the plurality of perforations formed along the outer tube 246 are configured to receive exhaust from the exhaust tract and direct the exhaust into the gap 226 formed between the inner and outer devices. Directing exhaust into the gap 226 includes directing the exhaust first into the space 228 between the outer tube 246 and the inner tube 248, as shown by arrow 279, and then into the gap 226, as shown by arrow 280. In particular, exhaust gas enters the space 228 via the plurality of holes 250 in a direction parallel to the exhaust flow direction (shown by arrow 258) within the exhaust tract 210.

[0055] As previously with reference to Fig. 2A, the upper surface 272 is sealed. Therefore, the exhaust gas within the space 228 is forced to travel downward (along the Y-axis, as shown by arrow 280) into the gap 226. Specifically, exhaust gas flows in a direction perpendicular (as shown by arrow 280) to each of the directions of exhaust flow within the exhaust tract 210 (as shown by arrow 258) and the exhaust flow direction into the space 228 (as shown by arrow 279). The exhaust gas then winds within the gap 226, within a region 232 enclosed within the gap 226, as shown by arrow 280. In the schematic view 290, the gap 226 is a ring formed between the inner and outer devices, such that the region 232 comprises an annular region within the gap 226. The exhaust gas within the gap 226 flows toward the lower portion of the spherical assembly 204.

[0056] Specifically, the exhaust gas within the gap 226 is split into two flow paths: a larger portion flowing toward the hole 244 formed at the lower portion of the inner device 218, and a smaller portion flowing toward the lower portion 261 of the inner device 218. Therefore, larger or heavier contaminants and / or water droplets 281 (such as particles larger than a threshold size or weight) in the exhaust gas can sink to the underside of the outer device 216 and flow into the hollow support rod 208 (as shown by arrow 283). Herein, the region 232 is fluidly coupled to the region 256 enclosed by the portion 254 of the hollow rod 208 located within the exhaust tract 210. Herein, the region 256 is a cylindrical region.In addition, the hollow rod 208 has a drainage hole 252 located closer to the bottom of the hollow rod 208, and the larger / heavier contaminants 281 can be directed out of the spherical assembly 204 through the drainage hole 252, as shown by arrow 285.

[0057] While larger and heavier contaminants 281 are directed to the hollow rod 208, a larger fraction or portion of the exhaust gas within the gap 226 is directed to the hole 244 formed on the underside of the internal device 218. Specifically, lighter soot particles in the exhaust gas are directed to the sensor element 234 suspended within the internal device 218, as indicated by arrow 282. The positioning of the hole 244 with respect to the sensor element 234 has several advantages. First, the hole 244 is positioned away from the plurality of perforations 250 of the flow tubes 206. This prevents problems with water droplets and larger contaminants at or near the perforations 250 from impinging on the sensor element. Second, the sensor element 234 is positioned above the hole 244, so the larger / heavier contaminants 281 present in the exhaust gas are directed away from the sensor element 234.As a result, the sensor surface is protected from larger contaminants and fluctuations in the sensor output can be reduced.

[0058] Therefore, exhaust gas flows through hole 244 from region 232 enclosed within gap 226 into region 230 enclosed within internal device 218. Region 230 includes a spherical region enclosed by internal device 218. Here, sensor element 234 is positioned within region 230 (and not within region 232, for example), and the exhaust gas is first directed to sensor element 234, as indicated by arrow 282. Specifically, lighter soot particles in the exhaust gas are directed upward (along the Y-axis), typically toward the surface of sensor element 234. In other words, the exhaust gas is directed in a direction perpendicular to a plane of sensor element 234 (e.g., along the X-axis).It will be appreciated that the exhaust gas is directed toward the first surface, which includes the electrode, rather than toward the second surface of the sensor element 234, which includes the heating element 238. Soot particles in the exhaust gas are collected between the interdigitated electrodes 236 of the sensor element 234, as previously described. Exhaust gas within region 230 is then directed upward (along the Y-axis, as indicated by arrow 284) to the inner tube 248, which is coupled to the top of the inner device 218. It will be appreciated that the exhaust flow direction in region 230 is opposite the exhaust flow direction in region 232. Further, the exhaust flow direction in region 230 is perpendicular to the exhaust flow direction in the exhaust tract 210 (arrow 258). Furthermore, the exhaust gas flow direction in the region 230 is perpendicular to the exhaust gas flow direction in the spherical arrangement 204 (arrow 279).

[0059] The exhaust gas in the region 230 enclosed within the inner device 218 flows upward (parallel to the central axis Y-Y', for example) into the inner tube 248 through the lower surface 278 of the inner tube 248. Specifically, exhaust gas flows from the region 230 into the cylindrical region 287 enclosed within the inner tube 248 through the lower surface 278. The exhaust gas then flows through the upper surface 274 of the inner tube 248 into the exhaust tract 210. Here, the exhaust gas flow direction out of the inner tube 248 is orthogonal to each of the exhaust gas flow directions within the exhaust tract 210 (as shown by arrow 258) and the exhaust gas flow direction into the spherical assembly 204 (as shown by arrow 279). In this way, by using the cylindrical flow tubes 206 configured with the outer tube and the inner tube, exhaust gas can be directed into or out of the spherical assembly 204.The symmetrical design of the inlet and outlet tube eliminates the manufacturing process for specific sensor orientation during installation and improves sensor reproducibility.

[0060] In short, exhaust gas flows through the perforations into a first region enclosed between the inlet and outlet pipes and is then directed to a second region enclosed in the gap between the inner and outer devices. In the same way, the exhaust gas in the second region enclosed by the gap is directed to a third, spherical region enclosed within the inner device, and additionally to a fourth, cylindrical region enclosed within the support rod. Here, the exhaust gas within the third region enclosed within the inner device is collected between the finger-like interlaced electrodes of the sensing element and then directed to a fifth, cylindrical region enclosed within the inner tube and then out into the exhaust tract.It will be appreciated that while the exhaust flow path is described in terms of areas, it can also be explained in terms of volumes. Herein, each of the areas above includes a specific volume; the first area encloses a first volume, and so on. Therefore, the exhaust flow can be explained interchangeably in terms of volumes.

[0061] Therefore, an exemplary particulate matter sensor includes a pair of concentric, finger-like interlaced electrodes formed on a first surface of a circular sensor element, a heating element formed on a second surface of the circular sensor element, the second surface opposite the first surface, support legs suspending the circular sensor element within an inner hollow, spherical guard, and an outer hollow, spherical guard for receiving the exhaust flow from an exhaust conduit and directing the exhaust flow to the circular sensor element, the inner guard being concentrically positioned within the outer guard.Additionally or alternatively, the outer protection device may include a mounting rod and an outer cylindrical tube coupled to diametrically opposed portions of the outer protection device, the mounting rod further coupling the outer protection device to a bottom of the exhaust conduit. Additionally or alternatively, a larger portion of the exhaust gas may be directed within the gap and redirected to an opening formed on the inner protection device, while a smaller portion of the exhaust gas may descend onto the mounting rod, wherein a size of the exhaust particles in the smaller portion is larger than the size of the exhaust particles in the larger portion.Additionally or alternatively, the larger exhaust portion captured at the opening and deflected into the inner shield may be directed to the pair of concentrically interlaced electrodes of the circular sensing element; and after passing through the sensing element, the larger exhaust portion may be directed into an inner cylindrical tube coupled to an upper portion of the inner shield. Additionally or alternatively, the inner cylindrical tube may be positioned coaxially within the outer cylindrical tube and configured to direct the larger exhaust portion out of the particulate matter sensor and into the exhaust conduit. Additionally or alternatively, the mounting rod may include a drainage hole coupled to the underside of the exhaust conduit to direct particulates in the smaller exhaust portion out of the particulate matter sensor and into the exhaust conduit.Additionally or alternatively, the mounting rod may include a drainage hole located closer to the bottom of the exhaust conduit to direct the particulate matter in the smaller exhaust portion out of the particulate matter sensor and into the exhaust conduit. Additionally or alternatively, the particulate matter sensor may further include a controller having computer-readable instructions stored on non-transitory memory for applying a positive and negative voltage to the pair of concentric, finger-interlaced electrodes to collect particulate matter in the larger exhaust portion between the pair of concentric, finger-interlaced electrodes and for estimating a load on the sensor based on a current generated between the pair of concentric, finger-interlaced electrodes of the circular sensor element.In response to the load being higher than a threshold, the controller can apply a voltage to the heating element to regenerate the sensor.

[0062] Fig. 2A-4 show example configurations with relative positioning of the various components. If shown directly touching or directly coupled to one another, such elements may, in at least one example, be referred to as directly touching or directly coupled, respectively. Likewise, elements that are contiguous or adjacent to one another in the illustration may, in at least one example, be contiguous or adjacent to one another, respectively. As one example, components that are in surface contact with one another may be referred to as being in surface contact with one another. As another example, elements that are spaced apart from one another, positioned with only a space and no other components between them, may, in at least one example, be referred to as such.As yet another example, elements shown above / below each other, on opposite sides of each other, or to the left / right of each other may be referred to as such with respect to each other. As shown in the figures, in at least one example, a topmost element or topmost point of an element may be referred to as a "top" of the component, and a bottommost element or bottommost point of the element may be referred to as a "bottom" of the component. As used herein, top / bottom, upper / lower, over / under may apply with respect to a vertical axis of the figures and may be used to describe the positioning of elements of the figures with respect to each other. Thus, in one example, elements shown above other elements are positioned vertically above the other elements.As another example, shapes of the elements shown in the figures may be referred to as having such shapes (such as circular, straight, planar, curved, rounded, shaved, angled, or the like). Further, in at least one example, elements shown intersecting may be referred to as intersecting elements or intersecting. Furthermore, in one example, an element shown inside another element or outside another element may be referred to as such.

[0063] With reference to Fig. 5, a method 500 is shown for collecting particulates in the exhaust stream over the sensor electrodes disposed within the FS sensor (such as an FS sensor 106 of Fig. 1 and / or the FS sensor arrangement 202 from the Fig. 2A and Fig. 2B). Specifically, the particulates in the exhaust stream can accumulate on the finger-like interdigitated electrodes formed on a circular substrate and positioned within a spherical protective assembly of the FS sensor. Herein, the spherical assembly includes an inner spherical device positioned within an outer spherical device and separated by a gap. Additionally, the spherical assembly includes a flow tube attached to the top for directing exhaust gas into and out of the spherical assembly.

[0064] Instructions for performing method 500 and the remaining methods 600 and 700 included herein may be executed by a controller based on instructions stored in a memory of the controller and in conjunction with signals received from sensors of the engine system, such as those described above with reference to the Fig. 1. The controller may use motor actuators of the engine system to adjust engine operation according to the methods described below.

[0065] At 502, method 500 includes determining and / or estimating engine operating conditions. Certain engine operating conditions may include, for example, engine speed, exhaust flow rate, engine temperature, exhaust air-fuel ratio, exhaust temperature, elapsed driving time (or distance traveled) since the last DPF regeneration, FS load on the FS sensor, boost pressure level, ambient conditions such as barometric pressure and ambient temperature, etc.

[0066] Method 500 proceeds to 504 where an exhaust gas portion collected from downstream of a particulate filter (PF; such as DPF 102 Fig. 1) flows into an FS sensor through perforations formed on an inlet tube. Herein, the inlet tube is an outer cylindrical tube having a plurality of perforations formed along the curved surface. Further, the cylindrical outlet tube may be positioned coaxially within the inlet tube and separated therefrom by a space. As previously explained, the inlet tube has a larger diameter than the outlet tube, but the length of the inlet tube is shorter than the length of the outlet tube. The exhaust gas portion flowing through the perforations of the inlet tube flows into a first region formed between the inlet and outlet tubes. Herein, the first region refers to the space between the inner and outer tubes. The first region encloses a first volume therebetween, the first volume being the volume enclosed in the space between the inlet and outlet tubes.The exhaust gas flow direction into the inlet pipe is parallel to the exhaust gas flow direction inside the outlet pipe, for example.

[0067] Next, method 500 proceeds to 506. At 506, method 500 includes directing the exhaust portion from the first volume to a second region in a direction orthogonal to the exhaust flow direction in the exhaust conduit. Herein, the second region refers to the gap between the inner and outer devices. For example, the first region is fluidly coupled to the second region through a bottom surface of the inlet tube.

[0068] Method 500 proceeds to 508. At 508, method 500 includes directing a larger portion of exhaust gas in the second region to a third region through a hole formed on the underside of the internal device. Herein, the third region is the region formed within the internal device that includes the sensor element. The sensor element is suspended within the internal device using support legs, for example. Thus, the exhaust flow direction from the second region to the third region is a direction opposite the exhaust flow direction within the second region. Additionally, the larger portion of exhaust gas includes particles having a size smaller than the threshold particle size (smaller particles, for example). Method 500 proceeds to 510.

[0069] At 510, method 500 includes collecting particulates in the larger exhaust portion on the electrodes of the sensing element. Specifically, at 510, the smaller particulates in the larger exhaust portion are directed toward the electrodes of the sensing element, and the smaller particulates are deposited on the electrodes. Here, the larger exhaust portion is typically directed toward the sensing element. Thus, the exhaust flow direction from the second region to the third region is orthogonal to the exhaust flow direction within the exhaust tract. As previously described, the sensing element with the interlaced electrodes is positioned closer to the hole. Therefore, smaller soot particles in the exhaust portion entering the third region through the hole are detected and collected on the concentric, interlaced electrodes of the sensing element.As previously described, the sensor electrodes can comprise finger-like interlaced main arcs or finger-like interlaced spiral electrodes. The positive electrodes are connected to the positive terminal of a power supply, and the negative electrodes are connected to a measuring device and then to the negative terminal of the power supply. When the controller applies a voltage to the sensor electrodes, the particles within the third region can experience a strong electric field, causing them to accumulate between the electrodes. In addition, a load on the sensor electrodes is estimated based on a current generated in the sensor electrodes. As particles accumulate on the surface of the sensor electrodes, the resistance of the electrodes begins to decrease, and a current measured by the measuring device begins to increase.The controller may be capable of deriving a load on the sensor electrodes based on the current measured across the electrodes. Method 500 then proceeds to 512.

[0070] Method 500 proceeds to 512. At 512, method 500 includes directing a smaller portion of exhaust gas within the second region to a fourth region, wherein the fourth region is formed within a hollow rod. While smaller particles in the exhaust gas are directed upward toward the hole and then toward the sensing element (e.g., at 508 and 510 in method 500), larger particles (such as particles larger than the threshold size) in the exhaust gas may sink to the bottom of the outer device at 512. Therefore, the smaller portion of exhaust gas and the larger portion of exhaust gas flow in opposite directions and further flow orthogonal to the exhaust flow direction in the exhaust conduit. As previously described, the hollow rod is fluidly coupled to the bottom of the outer device. Therefore, the larger particles that accumulate at the bottom of the outer device move into the fourth region enclosed by the hollow rod.Additionally, the hollow rod has a drainage hole located closer to the bottom of the hollow rod. Therefore, the larger particles in the smaller exhaust gas portion within the fourth region are directed to the drainage hole of the hollow rod and thus flow out of the assembly. In this way, by separating particles and directing the larger particles away from the sensing element and further directing the larger particles and water droplets to the drainage holes in the hollow rod, larger particles are unable to deposit on the sensing element. Therefore, sensor errors due to these particles depositing on the sensitive electrode surface can be reduced. The method proceeds to 514.

[0071] At 514, method 500 includes directing the larger exhaust portion within the third region formed within the internal device to a fifth region formed within the outlet tube in a direction orthogonal to the exhaust flow direction in the exhaust conduit. Directing the larger exhaust portion to the fifth region includes directing the larger exhaust portion from the third region of the internal device to the fifth region formed within the outlet tube through the bottom of the outlet tube coupled to the top portion of the internal device. Herein, the outlet tube is fluidly coupled to the top of the internal device, at an end disposed diametrically opposite the hole of the internal device, for example.Additionally, the larger portion of exhaust gas is directed from the fifth region and into the exhaust conduit through a top of the outlet tube in a direction orthogonal to the exhaust flow direction within the exhaust conduit. Method 500 then proceeds to 516.

[0072] At 516, method 500 includes intermittently checking whether the sensor electrode has met the regeneration conditions. Specifically, if the soot load at the FS sensor is greater than the threshold, or if a resistance of the FS sensor (set to temperature) drops to a threshold resistance, or if a current of the FS sensor is greater than a threshold current, the FS sensor regeneration conditions may be considered met. In some examples, if a threshold time has elapsed since an immediately prior sensor regeneration, the regeneration condition may be considered met. The FS sensor may require regeneration to enable further FS detection.

[0073] If the regeneration conditions are met (e.g., YES at 516), method 500 proceeds to 520 where the FS sensor is regenerated by performing a method described in Fig. 6. In short, the regeneration of the FS sensor can be initiated by heating the sensor. The FS sensor can be heated by actuating a heating element formed on another surface of the sensor element that is opposite the surface having the electrodes, for example. Herein, the controller can close the switch in a regeneration circuit and thus apply a voltage to the heating element, which causes the heating elements to heat up. Furthermore, the controller may not apply any voltages to the sensor electrodes while the sensor is regenerating. Therefore, the sensor electrodes may not accumulate soot during sensor regeneration. Therefore, the heating element can be actuated until the soot load of the sensor has been sufficiently reduced by oxidation of the carbon particles between the electrodes. However, if the FS sensor regeneration conditions are not met (e.g.,NO at 516), the method 500 goes to 518 where the particles can continue to be collected on the sensor electrodes and the method ends.

[0074] Therefore, an exemplary method may include flowing exhaust gas from downstream of a particulate filter into the exhaust sensor assembly through perforations formed on an inlet tube toward a first region formed between the inlet tube and an outlet tube in a direction parallel to exhaust gas flow in an exhaust conduit. Herein, the inlet tube may be coupled to a top of an outer hollow device, and the method may include directing exhaust gas from the first region to a second region formed between the outer device and an inner hollow device in a direction orthogonal to exhaust gas flow in the exhaust conduit. The inner device may be positioned concentrically within the outer device.Additionally or alternatively, the method may further comprise directing a larger portion of exhaust gas within the second region to a third region formed within the inner device through a hole positioned in a bottom side of the inner device in a direction opposite to the exhaust gas flow direction within the second region. The third region may include a sensor element suspended within the inner device. Additionally or alternatively, the method may further comprise directing a smaller portion of exhaust gas in the second region to a fourth region, wherein the fourth region is enclosed within a hollow rod of the sensor assembly, wherein the hollow rod may be coupled to a lower portion of the outer device.Additionally or alternatively, the method may further comprise applying a voltage to the concentric, finger-like interlaced electrodes of the sensor element to collect particulates in the larger exhaust gas portion between the electrodes and directing the larger exhaust gas portion first into a fifth region formed by an outlet pipe coupled to an upper end of the internal device and then out of the sensor assembly. Additionally or alternatively, the method may further comprise flowing particulates in the smaller exhaust gas portion within the fourth region to the drainage hole located at a lower end of the hollow rod and draining the particulates out of the drainage hole, the hollow rod coupling the exhaust gas sensor assembly to a bottom of the exhaust conduit.

[0075] With reference to Fig. 6 is a method 600 for regenerating the FS sensor (such as, for example, the FS sensor 106 of Fig. 1 and / or the FS sensor arrangement 201 from Fig. 2). In particular, if the soot load on the FS sensor is greater than the threshold or if a temperature-adjusted resistance of the FS sensor falls below a threshold resistance, the FS sensor regeneration conditions may be considered met and the FS sensor may require regeneration to enable further FS detection. At 602, FS sensor regeneration may be initiated and the FS sensor regenerated by heating the sensor at 604. The FS sensor may be heated by actuating a heating element until the sensor's soot load has been sufficiently reduced by oxidation of the carbon particles between the electrodes. FS sensor regeneration is typically controlled using timers, and the timer may be set to a threshold time period at 602.Alternatively, sensor regeneration may be controlled using a temperature measurement of the sensor tip or by controlling power to the heater, or any or all of these. If a timer is used for FS sensor regeneration, then method 600 includes checking at 606 whether the threshold time period has elapsed. If the threshold time period has not elapsed (e.g., NO at 606), then method 600 proceeds to 608, where the regeneration circuit may remain ON to continue regeneration and the method ends. If the threshold time period has elapsed (e.g., YES at 606), then method 600 proceeds to 610, where FS sensor regeneration may be aborted, and the electrical circuit may be deactivated at 612. Further, the sensor electrodes may be cooled, for example, to the exhaust gas temperature.Method 600 proceeds to 614, where the FS sensor load and regeneration history may be updated and stored in memory. For example, an FS sensor regeneration frequency and / or an average time between sensor regenerations may be updated, and the method ends.

[0076] The engine exhaust tract may include one or more FS sensors positioned upstream and / or downstream of the DPF for determining a soot load of the DPF. If the FS sensor is positioned upstream of the DPF, a soot load on the sensor may be derived based on the change in resistance after soot deposition on the multiple electrodes of the FS sensor. The soot load thus determined may, for example, be used to update the soot load on the DPF. If the soot load on the DPF is greater than a threshold for DPF regeneration, then the controller may adjust the engine operating parameters to regenerate the DPF. Specifically, in response to meeting the filter regeneration conditions, a temperature of the filter (or near the filter) may be increased sufficiently to burn off the stored soot. This may involve operating a heater coupled to the DPF or increasing the temperature of engine exhaust (e.g.,during heavy operation) that flows into the DPF.

[0077] With reference to Fig. 7 illustrates an example method 700 for diagnosing DPF function based on the FS sensor regeneration time. At 702, the controller may calculate, via calibration, the time of regeneration for the FS sensor, t(i)_regen, which is the time measured from the end of the previous regeneration to the start of the current FS sensor regeneration. At 704, t(i)_regen is compared to t(i-1)_regen, which is the previously calibrated FS sensor regeneration time. From this, it can be inferred that the soot sensor may run through a regeneration multiple times to diagnose the DPF. If t(i)_regen is less than half the value of t(i-1)_regen, then at 708, it is indicated that the DPF is leaking, and a DPF degradation signal is initiated. Alternatively, or in addition to the above-mentioned process, the DPF can be diagnosed using other parameters such as exhaust gas temperature, engine speed / load, etc.The degradation signal may be initiated, for example, by a malfunction indicator lamp or a diagnostic code. Additionally, method 700 includes adjusting engine operation based on the indication of a leak in the DPF at 710. Adjusting engine operation may include limiting engine torque at 712, for example. In one example, engine power and torque may be reduced in response to the detection of a leak in the DPF. By reducing engine power and torque, the amount of FS emissions in the exhaust may be reduced. Adjusting engine operation may include, for example, reducing fuel injected into a diesel engine under high load conditions, thus reducing torque. Additionally or alternatively, EGR utilization may be reduced in response to the detection of a leak in the DPF.Additionally or alternatively, an engine warning sign may appear on the control panel to indicate a maximum distance a vehicle can travel before a DPF service check.

[0078] A current regeneration time of less than half the previous regeneration time may indicate that the time required for the electrical circuit to reach the R_regen threshold is significantly shorter, thus requiring a higher regeneration frequency. A higher regeneration frequency of the FS sensor may indicate that the outgoing exhaust gas contains a larger amount of particulate matter than detected by a normally functioning DPF.Thus, if the change in regeneration time in the soot sensor reaches the threshold t_regen, at which the current regeneration time of the FS sensor is less than half the previous regeneration time, a DPF degradation or leak is indicated, for example, via an indication to an operator and / or by setting a flag stored in non-transitory memory coupled to the processor, which can be sent to a diagnostic tool coupled to the processor. If the change in regeneration time of the soot sensor does not reach the threshold t_regen, then no DPF leak is indicated at 706. In this way, leaks in a particulate filter positioned upstream of the particulate matter sensor can be detected based on a deposition rate of the particulate matter on the particulate matter sensor electrodes.

[0079] With reference to Fig. 8 shows the Fig. an exemplary relationship between the soot load on the FS sensor and the soot load on the particulate filter. Specifically, the Fig. A graphical representation of the relationship between FS sensor regeneration and soot load on the DPF, specifically how FS sensor regeneration can indicate DPF degradation. The vertical markers t0, t1, t2, t3, t4, t5, and t6 identify key times in the operation and system of the FS sensor and DPF.

[0080] The first diagram from Fig.Figure 8 shows a soot load on the FS sensor. As previously described, FS deposits on the circular positive and negative electrodes formed on a circular substrate positioned within an internal device closer to a hole formed on the bottom of the internal device, for example. As soot accumulates, a current measured across the electrodes begins to increase (or a resistance of the electrodes begins to decrease). The controller may be capable of determining a soot load (plot 802) based on the measured current / resistance. Therefore, the soot load is at its lowest value at the bottom of the plots and increases in magnitude toward the top of the plot in the vertical direction. The horizontal direction represents time, and time increases from the left side to the right side of the plot. The horizontal marker 806 represents the threshold load for regenerating the FS sensor in the upper plot.Diagram 804 represents the soot load on the DPF and the horizontal mark 808 represents the threshold soot load of the DPF in the second diagram.

[0081] Between t0 and t1, an FS sensor regeneration cycle is depicted. At time t0, the FS sensor is in a relatively clean condition, as measured by the low FS load (chart 802). A controller coupled to the FS sensor determines the FS sensor's soot load based on the current / resistance measured across the sensor electrodes, for example. If the controller determines the soot load to be low, it can send instructions to a regeneration circuit to stop heat application so that a detection circuit can begin detecting FS load accumulation. As the FS load on the sensor increases, soot accumulates in the gap between the sensor electrodes.

[0082] Between t0 and t1, FS continues to accumulate, and the soot load (plot 802) and the soot load on the DPF (plot 804) increase accordingly. In some examples, the soot load on the DPF may be based on the FS sensor load, for example, if the FS sensor is located upstream of the DPF.

[0083] At t1, the soot load on the FS sensor (plot 802) reaches the threshold load for FS sensor regeneration (marker 806). The threshold load may be a load at which the sensor may require regeneration. At t1, FS sensor regeneration may be initiated as previously explained. Briefly, the controller may close a switch in the electrical circuit for applying voltage to the heating elements formed along the inner surface of the central element, for example. Additionally, the FS sensor may not be operating in FS accumulation mode, so the controller cannot apply voltage to the sensor electrodes.

[0084] Therefore, between t1 and t2, the FS sensor may be regenerated by switching on the electrical circuit for regeneration. At t2, the FS sensor may be sufficiently cool and may begin to accumulate soot and continue to accumulate between t2 and t3 (DPF regeneration cycle), for example. During the time between t2 and t3, the DPF soot load continues to increase (plot 804). However, at t3, the soot load on the DPF (plot 804) reaches the threshold soot load for DPF regeneration (marker 808). Between t3 and t4, the DPF may be regenerated to burn off soot deposited on the DPF. Furthermore, at t4, the FS sensor regeneration frequency may be compared to a previously estimated FS sensor regeneration frequency. Based on the FS sensor regeneration frequency remaining similar to previous cycles, the DPF can be determined to be non-leaking.In this way, based on the FS sensor output, DPF health can be monitored and checked for leaks.

[0085] Between t5 and t6, another DPF cycle is shown. Here, between t5 and t6, the soot load on the DPF gradually increases (plot 804). During this time, the soot load on the FS sensor (plot 802) can be monitored. Plot 802 shows the FS sensor running through the multiple regeneration cycles as previously described. However, the regeneration frequency of the FS sensor has almost doubled (plot 802). A higher regeneration frequency in the FS sensor may indicate that the outgoing exhaust gas is composed of a larger amount of particulate matter than detected with a normally functioning DPF. Therefore, DPF leakage may be indicated at t6.

[0086] This allows for a more precise measurement of the exhaust gas FS load and thus the DPF soot load. This increases the efficiency of filter regeneration processes. Furthermore, by enabling more accurate diagnosis of an exhaust DPF, exhaust emission compliance can be improved. This reduces the high warranty costs of replacing functioning particulate filters and extends the service life of exhaust components.

[0087] In this way, the sensor element can be shielded by two spherical protective tubes, which further improves uniform soot deposition. Exhaust gases can enter the sensor assembly through perforations formed in the outer inlet tube. Therefore, the exhaust gas can undergo changes in flow direction, which can reduce the flow rate. Additionally, the exhaust gas can be directed to the sensor element positioned within the inner device through a hole formed on the underside of the inner device. Here, the hole can be spaced from the inlet tube to separate the inlet tube from the sensor element. In this way, by separating the inlet tube from the sensor element, problems regarding water droplets and larger contaminants impacting the sensor element and causing fluctuations in the sensor output can be reduced.Furthermore, the hole on the internal device can be sized, shaped and positioned to create a uniform flow of exhaust gases onto the sensor surface.

[0088] The technical effect of a more uniform flow impingement of exhaust gas samples onto a particulate matter sensor can be achieved by reducing the exhaust gas flow velocity. By interrupting the exhaust gas flow path and reducing the velocity, the flow uniformity over the particulate matter sensor surface can be increased. Furthermore, by positioning the sensor element away from the inlet pipe and additionally mounting the assembly on a hollow rod, the particulate matter sensor can be shielded from contamination by larger particles and water droplets. Furthermore, the drainage holes on the underside of the hollow rod can guide contaminants out of the sensor assembly.

[0089] The systems and methods described above provide a particulate matter sensor assembly comprising a spherical assembly, a support rod coupled to a lower end of the spherical assembly, a plurality of flow tubes coupled to an upper end of the spherical assembly, and a sensor element disposed within the spherical assembly distal from the plurality of flow tubes. In a first example of the particulate matter sensor assembly, the sensor may additionally or alternatively include the spherical assembly comprising a hollow inner device concentrically positioned within a hollow outer device, the inner device being separated from the outer device by a gap.A second example of the particulate matter sensor assembly optionally includes the first example and further includes wherein the plurality of flow tubes comprise an outer cylindrical tube and an inner cylindrical tube coaxially disposed within the outer tube, wherein a length of the outer tube is less than a length of the inner tube. A third example of the particulate matter sensor assembly optionally includes one or more of the first and second examples and further includes wherein the outer tube is mounted on an upper end of the spherical assembly through the hollow outer device.A fourth example of the particulate matter sensor assembly optionally includes one or more of the first to third examples, and further includes the outer tube having a plurality of perforations configured to receive exhaust gas from an exhaust tract, the exhaust gas being received in the gap between the outer device and the inner device in a direction orthogonal to a plane of the sensor element, the exhaust gas then being directed through the gap to a hole formed along a lower portion of the inner device, the hole being configured to direct the exhaust gas from the gap into the inner device toward the sensor element in a direction opposite to an exhaust gas flow direction through the gap.A fifth example of the particulate matter sensor assembly optionally includes one or more of the first to fourth examples, and further includes the sensor element comprising a pair of circular, finger-intertwined electrodes formed on a first surface and a heating element formed on a second, opposite surface, wherein the sensor element is floatingly coupled within the internal device by support legs coupled to the internal device such that the pair of circular, finger-intertwined electrodes face the hole on the internal device, and wherein the pair of circular, finger-intertwined electrodes comprise finger-intertwined, spiral-shaped positive and negative electrodes.A sixth example of the particulate matter sensor assembly optionally includes one or more of the first to fifth examples, and further includes that the inner tube is mounted to the upper end of the spherical assembly through a hollow inner device such that the inner device traverses the gap in the spherical assembly, wherein the exhaust gas received by the outer tube and directed into the inner device is discharged through the inner tube into the exhaust tract.A seventh example of the particulate matter sensor assembly optionally includes one or more of the first to fifth examples, and further includes that the support rod is hollow and couples the spherical assembly to a bottom of an exhaust tract, and that the support rod is configured to direct an exhaust portion captured in the gap into the exhaust tract through a drainage hole of the support rod, the drainage hole being positioned proximate the bottom of the exhaust tract, the exhaust portion comprising exhaust particles having a size greater than a threshold size.

[0090] The systems and methods described above provide a system comprising a particulate matter (PPM) sensor disposed downstream of a particulate filter in an exhaust tract, the PPM sensor comprising a pair of concentric, finger-like interleaved electrodes formed on a first surface of a circular sensor element, a heating element formed on a second surface of the circular sensor element, the second surface being opposite the first surface, support legs suspending the circular sensor element within an inner hollow, spherical guard, and an outer hollow, circular guard for receiving exhaust flow from an exhaust conduit and directing exhaust flow to the circular sensor element, the inner guard being concentrically positioned within the outer guard.In a first example of the particulate matter sensor, the sensor may additionally or alternatively include the outer guard having a mounting rod and an outer cylindrical tube coupled to diametrically opposed portions of the outer guard, the mounting rod further coupling the outer guard to a bottom of the exhaust conduit. A second example of the particulate matter sensor optionally includes the first example and further includes the outer cylindrical tube comprising a plurality of holes configured to direct exhaust gas from the exhaust conduit first into a gap between the inner guard and the outer guard.A third example of the particulate matter sensor optionally includes one or more of the first and second examples, and further includes wherein a larger portion of exhaust gas directed within the gap is deflected toward an opening formed on the inner guard while a smaller portion of exhaust gas descends onto the mounting rod, wherein a size of the exhaust particles in the smaller portion is larger than the size of the exhaust particles in the larger portion.A fourth example of the particulate matter sensor optionally includes one or more of the first to third examples, and further includes directing the major exhaust gas portion received at the opening and diverted into the inner shield to the pair of concentric and interdigitated electrodes of the circular sensing element; and, after passing through the sensing element, directing the major exhaust gas portion into an inner cylindrical tube coupled to an upper portion of the inner shield. A fifth example of the particulate matter sensor optionally includes one or more of the first to fourth examples, and further includes the inner cylindrical tube being coaxially positioned within the outer cylindrical tube and configured to direct the major exhaust gas portion out of the particulate matter sensor and into the exhaust conduit.A sixth example of the particulate matter sensor optionally includes one or more of the first to fifth examples, and further includes that the mounting rod has a drainage hole coupled to the bottom of the exhaust conduit to direct particulates in the minor exhaust portion out of the particulate matter sensor and into the exhaust conduit.A seventh example of the particulate matter sensor optionally includes one or more of the first to sixth examples and further comprises a controller having computer readable instructions stored on a non-transitory memory for applying a positive and negative voltage to the pair of concentric, finger-interlaced electrodes to accumulate particulate matter in a larger portion of exhaust gas between the pair of concentric, finger-interlaced electrodes, and for estimating a load of the sensor based on the current generated between the pair of concentric, finger-interlaced electrodes of the circular sensing element, and in response to the load being higher than a threshold, applying a voltage to the heating element to regenerate the sensor.

[0091] The systems and methods described above also provide a method comprising: flowing exhaust gas from downstream of a particulate filter into the exhaust gas sensor assembly through perforations formed on an inlet tube toward a first region formed between the inlet tube and an outlet tube in a direction parallel to exhaust gas flow in an exhaust conduit, the inlet tube being coupled to an upper one of an outer hollow device, and directing exhaust gas toward a second region formed between an outer device and an inner hollow device in a direction orthogonal to exhaust gas flow in the exhaust conduit, the inner device being concentrically positioned within the outer device.In a first example of the method, the method may additionally or alternatively include: directing a larger portion of exhaust gas within the second region to a third region formed within the inner device through a hole formed in a bottom side of the inner device in a direction opposite to the exhaust gas flow direction within the second region, wherein the third region has a sensor element suspended within the inner device, and directing a smaller portion of exhaust gas in the second region to a fourth region, wherein the fourth region is enclosed within a hollow rod of the sensor assembly, the hollow rod being coupled to a lower portion of the outer device.A second example of the method optionally includes the first example and further includes applying a voltage to the concentric, finger-like interlaced electrodes of the sensor element to collect particulates in the larger exhaust portion between the electrodes and directing the larger exhaust portion first into a fifth region formed by an outlet pipe coupled to an upper end of the internal device and then out of the sensor assembly. A third example of the method optionally includes one or more of the first and second examples and further includes flowing particulates in the smaller exhaust portion within the fourth region to a drainage hole located at a lower end of the hollow rod and discharging the particulates at the drainage hole, wherein the hollow rod couples the exhaust sensor assembly to a bottom of the exhaust conduit.

[0092] It should be noted that the example control and estimation routines included herein may be used with various engine and / or vehicle system configurations. The control methods and routines disclosed herein may be stored as executable instructions in non-volatile memory and may be executed by the control system comprising the controller combined with the various sensors, actuators, and other engine hardware. The specific routines described herein may represent one or more of any number of processing strategies, such as event-driven, interrupt-driven, multitasking, multithreading, and the like. Therefore, various operations, sequences, and / or functions may be performed in the illustrated order, in parallel, or in some cases, omitted.Likewise, the order of processing is not necessarily required to achieve the features and advantages of the embodiments described herein, but is provided for ease of illustration and description. One or more of the illustrated operations, procedures, and / or functions may be performed repeatedly depending on the particular strategy employed. Furthermore, the described operations, procedures, and / or functions may graphically represent code to be programmed into non-transitory memory of the computer-readable storage medium in the machine control system, wherein the described operations are performed by executing the instructions in a system including the various machine hardware components in combination with the electronic controller.

[0093] It is understood that the configurations and routines disclosed herein are exemplary in nature, and that these specific embodiments are not to be considered limiting, as numerous variations are possible. For example, the above technology may be applied to V-6, I-4, I-6, V-12, horizontally opposed four, and other engine types. The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations, and other features, functions, and / or characteristics disclosed herein.

[0094] The following claims particularly point out certain combinations and subcombinations that are considered novel and non-obvious. These claims may refer to "a" element or "a first" element, or the equivalent thereof. Such claims should be understood to encompass the inclusion of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and subcombinations of the disclosed features, functions, elements, and / or properties may be claimed by amending the present claims or by presenting new claims in this or a related application. Such claims, whether broader, narrower, the same, or different in scope from the original claims, are also considered to be included within the subject matter of the present disclosure.

Claims

[1] Particulate matter sensor assembly (202) comprising: a spherical arrangement (204); a support rod (208) coupled to a lower end of the spherical assembly (204); a plurality of flow tubes (206) coupled to an upper end of the spherical assembly (204); and a sensor element (234) positioned within the spherical array (204) distal to the plurality of flow tubes (206). [2] The assembly of claim 1, wherein the spherical assembly (204) comprises a hollow inner device (218) concentrically positioned within a hollow outer device (216), the inner device (218) being separated from the outer device (216) by a gap (226). [3] The assembly of claim 2, wherein the plurality of flow tubes (206) comprise an outer cylindrical tube (246) and an inner cylindrical tube (248) coaxially disposed within the outer tube (246), a length of the outer tube (246) being less than a length of the inner tube (248). [4] The assembly of claim 3, wherein the outer tube (246) is mounted through the hollow outer device (216) at the upper end of the spherical assembly (204). [5] The assembly of claim 3 or claim 4, wherein the outer tube (246) has a plurality of perforations (250) configured to receive exhaust gas from an exhaust tract (210), the exhaust gas being received in the gap (226) between the outer device (216) and the inner device (218) in a direction orthogonal to a plane of the sensor element (234), the exhaust gas then being directed through the gap (226) to a hole (244) formed along a lower portion (266) of the inner device (218), the hole (244) being configured to direct the exhaust gas from the gap (226) into the inner device (218) toward the sensor element (234) in a direction opposite to an exhaust gas flow direction through the gap (226). [6] The assembly of claim 5, wherein the sensor element (234) comprises a pair of circular, finger-like interlaced electrodes (236) formed on a first surface and a heating element (238) formed on a second, opposite surface, wherein the sensor element (234) is suspendably coupled within the inner device (218) by support legs (242) coupled to the inner device (218) such that the pair of circular, finger-like interlaced electrodes (236) face the hole (244) of the inner device (218), and wherein the pair of circular, finger-like interlaced electrodes (236) comprise finger-like interlaced, spiral positive and negative electrodes. [7] An assembly according to claim 5 or claim 6, wherein the inner tube (248) is mounted at the top of the spherical assembly (204) through the hollow inner device (218) such that the inner tube (248) traverses the gap (226) in the spherical assembly (204), wherein the exhaust gas received by the outer tube (246) and directed into the inner device (218) is discharged through the inner tube (248) into the exhaust tract (210). [8] The assembly of any one of claims 5 to 7, wherein the support rod (208) is hollow and couples the spherical assembly (204) to a bottom surface (212) of the exhaust tract (210), and wherein the support rod (208) is configured to direct an exhaust gas portion received in the gap (226) into the exhaust tract (210) through a drainage hole (252) of the support rod (208), the drainage hole (252) being positioned proximate the bottom surface (212) of the exhaust tract (210), the exhaust gas portion comprising exhaust particles having a size greater than a threshold size. [9] Particulate matter sensor, which includes: a pair of concentric, finger-like interlaced electrodes (236) formed on a first surface of a circular sensor element (234); a heating element (238) formed on a second surface of the circular sensor element (234), the second surface being opposite the first surface; Support legs (242) suspending the circular sensor element (234) within an inner, hollow, spherical protective device; and an outer, hollow, circular guard for receiving the exhaust gas flow from an exhaust conduit and for directing the exhaust gas flow to the circular sensor element (234), the inner guard being concentrically positioned within the outer guard. [10] The particulate matter sensor of claim 9, wherein the outer protection device comprises a mounting rod and an outer cylindrical tube (246) coupled on diametrically opposed portions of the outer protection device, the mounting rod further coupling the outer protection device to a bottom of the exhaust conduit. [11] The particulate matter sensor of claim 10, wherein the outer cylindrical tube (246) includes a plurality of holes (250) configured to direct exhaust gas from the exhaust conduit into a gap (226) between the inner guard and the outer guard. [12] The particulate matter sensor of claim 11, wherein a larger portion of the exhaust gas directed within the gap (226) is deflected toward an opening (244) formed on the inner guard, while a smaller portion of the exhaust gas descends onto the mounting rod, a size of the exhaust particles in the smaller portion being larger than the size of the exhaust particles in the larger portion. [13] The particulate matter sensor of claim 12, wherein the major portion of the exhaust gas received at the aperture (244) and deflected into the inner shield is directed to the pair of concentrically interdigitated electrodes (236) of the circular sensing element (234); and after passing through the sensing element (234), the major portion of the exhaust gas is directed into an inner cylindrical tube (248) coupled to an upper portion of the inner shield. [14] The particulate matter sensor of claim 13, wherein the inner cylindrical tube (248) is coaxially coupled within the outer cylindrical tube (246) and is configured to direct the major portion of exhaust gas out of the particulate matter sensor and into the exhaust conduit. [15] A particulate matter sensor according to any one of claims 12 to 14, wherein the mounting rod has a drainage hole (252) coupled to the underside of the exhaust conduit for directing the particles in the minor exhaust gas portion out of the particulate matter sensor and into the exhaust conduit. [16] A particulate matter sensor according to any one of claims 12 to 15, further comprising a controller having computer-readable instructions stored in a non-transitory main memory for: Applying a positive and negative voltage to the pair of concentric, finger-like interlaced electrodes (236) to collect particulates in the larger exhaust gas portion between the pair of concentric, finger-like interlaced electrodes (236); Estimating a load of the particulate matter sensor based on the current generated between the pair of concentrically interlaced electrodes (236) of the circular sensor element (234); and in response to the load being higher than a threshold, applying a voltage to the heating element (238) to regenerate the particulate matter sensor.

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